X.500

Directory services based on X.500 inlude

• Microsoft's Active Directory
• Lightweight Directory Access Protocol (LDAP)
• Novell eDirectory
• Siemens DirX

The Domain Name System (DNS) is a directory service which is not based on X.500.

X.509 was originally intended to be based on X.500.

There are two kinds of objects

• Organisational Units (OU), which is a container object
• Leaf objects, which are contained in containers (CN, UID, etc.)

ISO/IEC 9594-1:2020 Information technology — Open systems interconnection — Part 1: The Directory: Overview of concepts, models and services